Production of o2 from co2 by electric arc or radiant energy



1'. l. TAYLOR 3,113,086 PRODUCTION OF 03 FROM CO3 BY ELECTRIC ARC OR RADIANT ENERGY Filed Jan. 29, 1959 m m mm m R m E w 0 3E8. v Y w w g m p A 1 w N 8 iv 5 mm m v 7 mmzmommewfi 6 6 m A |l.|vl| nu N u Al ub mm m v wt Aw w United States Patent 3,113,086 PRUDUCTIGN OF 0 FRGM C0 BY ELECTRIC ARC 0R ENERGY Thomas Evan Taylor, Leonia, N1, assignor to is'omet Corporation, Palisades Park, N.J., a corporation of New Jersey Filed Jan. 2% 1959, Ser. No. 789,998 4 Claims. (6!. 204-164) This invention relates to a cyclic process for treating carbon dioxide to produce 0 It has particular application in treating CO that accumulates as a result of animal respiration in an enclosure, for example, in the interior of a submarine or a space vehicle.

When a submarine is submerged or a manner space vehicle is in flight, its occupants depend on oxygen tanks for their supply of oxygen. With each respiration a quantity of oxygen is removed from the atmosphere, and a quantity of CO is added. Unless fresh oxygen is supplied, and excess CO removed, the atmosphere of the vehicle soon becomes incapable of supporting life. The present invention provides a method of reacting the undesired CO to produce 0 thus removing CO concurrently with conversion of CO to 0' and thereby concurrently effecting two kinds of revitalization of exhausted air.

It is an object of the present invention to provide a cyclic process for the conversion of CO to C and 0 It is also an object of the present invention to provide a cyclic process for removing CO gas from a confined space and replacing same by 0 by converting the CO into C and 0 It is a further object of the present invention to provide a process for converting CO to- C and O which-utilizes a radiant energy to convert gaseous CO to CO and O and which utilizes a catalyst for converting CO to CO and C, which CO is then recycled to the radiant energy treatment step.

It is another object of the invention to provide a process for converting gaseous CO to O and C by (1) converting the CO to CO and O in an. electric arc, (2) separating. the CO from the O (3) converting the CO to C and C0 (4) separating the C and CO and (5) resupplying the CO to the electric are for further conversion to CO and 0 Other and more, detailed objects, features and advantages of the present invention will become apparent upon consideration of the following description, claims and drawings, wherein:

The single FIGURE is a flow diagram of a process according to the present invention.

Briefly describing a preferred embodiment of the present invention, a stream of CO containing gas is subjected to the action of radiant energy, e.g. electric discharge, short ultra-violet rays or nuclear radiation, and preferably to electric discharge, which converts the CO to CO and 0 The gas mixture resulting from the reaction is then passed through a gas separation system, which preferentially separates 0 CO and CO from each other. The gas stream containing the CO is converted to C in powder form and CO by means of a catalyst. The carbon powder is separated out and the gas mixture containing CO is recycled to the radiant energy treatment step. The O picked up by the separation system preferably is combined with a solid. The latter is readily removed from the system and the O regenerated in any suitable manner and returned to the atmosphere. The separated carbon may be recovered and pressed into bricks or pellets. The net result is the conversion of CO to C and 0 In one aspect of the present invention an electric discharge tube producing an arc is used in converting CO increase the yield of O The yield of 0 may also be.

increased by using dry CO gas.

The CO and 0 produced in the discharge tube in the vicinity of the arc tend to recombine to form CO It is therefore advantageous to cool the gases above the arcquickly. This is accomplished by the rapid removal of the gases from above the are by means of a circulation pump, or by leaving the flow path immediately above the arc unimpeded. A cool surface of inactive material above the arc, against which the gases leaving the arc may impinge, may also serve to cool the gases.

The 0 formed in the electric discharge tube is removed from the system before the gases are again recycled to the electric discharge tube. For this purpose any of a large number of agents may be used to take up the oxygen. Thus, for example BaO, complex cobalt compounds, e.g., cobalt chelates. Alternatively the socal'led molecular sieve, or other similar absorbent may be used in the well known chromatographic separation methods.

Among the complex cobalt compounds may be. mentioned the cobalt chelates capable of carrying oxygen (see Bailor-Chemistry of the Coordination Compounds, 1956, pages 45 to 47, and the articles by Calvin et al. in the Journal of The American Chemical Society, vol. 68, pages 2254 to 2256, 2257 to 2262, 2263 to 2266, 2267 to 2273, 2273 to 2278 and 2612 to 2618.

In accordance with the present invention the CO formed in the electric discharge tube is converted into.

CO and C, the CO being recycled to the electric discharge tube. To effect this conversion a suitable catalyst is employed such as Ni, Co. Fe, Pt or the like or catalysts containing the same. The conversion of CO to C and CO may be efiected over a relatively wide temperature range which will vary with the catalyst and other process conditions such as pressure or presence of water vapor. However, best results may be obtained in the temperature range of about 350'450 C.

The rate of flow of gases through the system may vary considerably according to the size of the installation, and the reaction condition. By way of example, flow rates of 250 cc./min. or 1000' cc./min. in laboratory equipment were found operative, the greater yield of 0 per minute being obtained at the upper end of the range.

time lag between the starting of the operation and the point of maximum rate of 0 produced.

Referring to the drawing, which shows a schematic representation of an illustrative embodiment of the present invention, the system comprises four sections; (I) the CO decomposition section; (II) the residual CO removal section; (III) the O absorption section, and (IV) the CO conversion section.

Section I comprises a two liter flask 1 having a long neck which has an outer diameter of about 40 mm. Approximately midway down neck 3 is discharge tube 5, whose interior is continuous with the interior of neck 3. Each end of discharge tube 5 is provided with an electrode 7. In the apparatus illustrated the electrodes are of platinum and the discharge tube has an outside diameter of 18 mm., the spark gap between the electrodes being about 2 cm. The platinum electrode may be replaced with a nickel electrode, or any other electrode may be employed which is capable of producing and maintaining, an electrical arc over a considerable period. The electrodes are connected to transformer 9, by means of electrical leads Patented Dec. 3, 1963 3 11. The transformer employed may be of 100-300 Watt capacity and 12,000 to 15,000 volts output.

In operation, CO gas is introduced into flask 1 through line 2. The CO may be obtained by the vaporization of Dry Ice, although any other suitable CO source may be used. If wet, the CO gas is dried, by any suitable and conventional means, before it enters flask 1. Current is then turned on and an arc is developed between the electrodes. The CO gas traversing the arc is partially converted into CO and O in accordance with the equation The product gases together with unconverted CO are rapidly led away from the arc and out of flask 1 to section II. This is effected by the pumping system.

Section I of the system is joined to section II of the system by means of conduit 13. Section II is designed to remove residual CO from the system preliminary to removing from the system. For this purpose is provided a tubular system 15 having two branches 17 and 19, each provided with molecular sieves, i.e., zeolite type absorbents. In place of the molecular sieves other CO absorbents such as silicagel or carbon may be used.

The gases entering section II by means of line 13 are 0 CO and residual CO For some purposes, it is advantageous to remove the residual CO first. The mixture of gases are passed through, for example, line 15 of section 11 while valves 21 and 23 are closed. CO is strongly absorbed by molecular sieve and CO is next strongly absorbed, whereas passes through readily. The gases are passed through the arm 19 until gauge 25 indicates that CO is starting to come through. The valving is then switched so that valves 21 and 23 are open and valves 29 and 31 are closed. The gases are thereby directed through arm 17. The material in arm 19 is then heated to drive off the CO During this operation valve 33 is left open and the CO evolved is recycled by line 35 to the CO feed line 2. Similarly, when gauge 27 begins to indicate that CO is starting to come through, valves 21 and 23 are closed and valve 22 is opened. Arm 17 is then heated to drive off the CO which is then recycled by means of line 26 to feed line 2.

Section II of the system is joined to section III of the system by means of conduit 37, which carries a mixture of CO and O to O absorbing chamber 39. Maintained in chamber 39 is a bed of BaO 41 which permits the gases to pass therethrough. The O rising through chamber 39 reacts with BaO in accordance with the equation The BaO is removed from the bottom of chamber 39 by means of line 43 and may be regenerated into oxygen in a suitable manner. The CO rising in chamber 39 leaves the chamber by means of line 45. In place of the 3210 bed other 0 absorbers may be employed. Notable among these are the cobalt chelates, such as cobalt salicylaldehyde ethylenediimine and the like.

Section II of the system is designed to remove CO from the system prior to O removal. This is usually preferable since it has been found that with certain 0 absorbents the presence of CO in the gas stream interferes with O absorption by these absorbents. However, where absorbents are employed such that the presence of CO is not disadvantageous section II might be dispensed with, and the gases issuing from section I may be led directly to O absorption section III.

Alternatively, section III may be dispensed with if an absorbent such as molecular sieve absorbent in Section II is operated at a low temperature. In this case, the gases come through conduit 17 in the order 0 CO and CO With valves 61 and 63 closed, 0 may be drawn off through valve 62. When the meter 27 indicates that CO has started to come through the absorbent, valve 62 is closed and valve 63 is opened. Then when CO starts i to come through 119 is used, valve 22 is opened, valve 23 and 63 are closed and I7 is heated to drive off the CO This cycle is then repeated while the gases come through 119.

The gas stream leaving chamber 39 by line 45 is rich in CO. It is a feature of this invention to convert this CO to CO which can be reprocessed to produce additional 0 To this end, the gas stream containing the CO is conveyed to section IV of the system, comprising a quartz tube 47 having an outside diameter of 30 1pm., containing nickel screen material 49, which serves as a catalyst. About the center of tube 47 is an electrical furnace 51, which may be regulated by the voltage varying means 55. The temperature is maintained at between 300 to 350 C. However, it may be operated in a wider temperature range of from 300 to 450 C. During the reaction carbon collects in the tube. When the carbon deposits become extreme a fresh tube containing nickel screen catalyst is inserted in the system.

The reaction that takes place in section IV may be expressed by the equation:

catalyst heat The CO produced in this reaction is recycled through line 59 by means of pump 60 to CO feed line 2, thus completing the cycle.

Using the apparatus described above and the conditions set forth therein the following runs were made:

CO COz-i-C Flow rate of C02, ce./ Tii11e,min. Percent 02 The approximate rate of production of 0 under flow conditions of about 200 to 250 cc./min. is 5 to 6.3 cc./ min. and for a flow rate of about 1000 cc./min., 14 cc./min.

While I have described and illustrated the present invention as employed in a preferred embodiment utilizing an electric arc, the latter may be replaced by a source of strong ultra-violet electromagnetic wave energy, with Wave length shorter than 1700 A. Where the invention is employed in a submarine the electric arc presents the most practicable and suitable device for decomposing CO whereas in a space vehicle, electrical power is not generally available in excess of requirements, whereas abundant u1tra-violet radiation is available, and is therefore employed. Nuclear radiations may also be used for decomposing the CO for special purposes.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the general arrangement and of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. Process for the conversion of CO to 0 which comprises the steps of passing a C0 containing gas through an electric discharge to dissociate the CO into CO and O rapidly removing and cooling the mixture of CO, 0 and undissociated (30 thus formed, removing CO from the mixture by passing the mixture through a solid absorbent for the CO passing the resulting mixture of (IO and 0 through a solid absorbent for the 0 contacting the CO with a metal catalyst of group VIII of the periodic system at an elevated temperature to transform the CO into free carbon and CO regenerating the 5 CO from its absorbent, recycling all the CO to the electric discharge treatment step, and recovering the 0 from its absorbent.

2. The process of claim 1 in which the absorbent for the CO is a zeolite bed.

3. The process of claim 1 in which the electric discharge is an electric arc.

4. Process for the conversion of CO to 0 which comprises the steps of passing a C0 containing gas through an electric discharge to dissociate the CO into CO and O rapidly removing and cooling the mixture of CO, 0 and undissociated CO thus formed, removing 0 from the mixture by passing the mixture through a solid absorbent for the 0 passing the resultin mixture of CO and CO in contact with a metal catalyst of group VIII of the periodic system at an elevated temperature to trans form the CO into free carbon and CO recycling all the CO to the electric discharge treatment step, and recovering the 0 from its absorbent.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES 10 I. Amn. Chem. 800., vol. 47 (1925), pp. 2682, 2684 and 2690. (Copy in Div. 6.)

J. Chem. Soc., page 133 (1948).

Ellis et al.: The Chemical Action of Ultraviolet Rays,

pp. 45, 307 and 308 (1941).

(Copy in Div. 56.)

15 Glockler et al.: The Electrochemistry of Gases and Other Dielectrics, pp. 233238 (1939). Div. 56.)

( py in 

1. PROCESS FOR THE CONVERSION OF CO2 TO2 WHICH COMPRISES THE STEPS OF PASSING A CO2 CONTAINING GAS THROUGH AN ELECTRIC DISCHARGE TO DISSOCIATE THE CO2 INTO CO AND O2, RAPIDLY REMOVING AN DCOOLING THE MIXTURE OF CO, O2 AND UNDISSOCIATED CO2 THUS FORMED, REMOVING CO2 FROM THE MIXTURE BY PASING THE MIXTURE THROUGH A SOLID ABSORBENT FOR THE CO2, PASSING THE RESULTING MIXTURE OF CO AND 32 THROUGH A SOLID ABSORBENT FOR THE 32, CONTACTING THE CO WITH A METAL CATALYST OF GROUP VIII OF THE PERIODIC SYSTEM AT AN ELEVATED TEMPERATURE TO TRANSFORM THE CO INTO FREE CARBON AND CO2, REGENERATING THE CO2 FROM ITS ASBORSOEBENT, RECYCLING ALL THE CO2 TO THE ELECTRIC DISCHARGE TREATMENT STEP, AND RECOVERING THE O2 FROM ITS ABSORBENT. 